This relates generally to imaging systems, and more particularly, to imaging systems with modified clear image pixels.
Image sensors are commonly used in electronic devices such as cellular telephones, cameras, and computers to capture images. In a typical arrangement, an electronic device is provided with an array of image pixels arranged in pixel rows and pixel columns. Circuitry is commonly coupled to each pixel column for reading out image signals from the image pixels.
Conventional imaging systems employ an image sensor in which the visible light spectrum is sampled by red, green, and blue (RGB) image pixels arranged in a Bayer mosaic pattern. The Bayer mosaic pattern consists of a repeating cell of two-by-two image pixels, with two green pixels diagonally opposite one another, along with a red pixel and a blue pixel that are diagonally opposite one another.
Some imaging systems replace the green color filters in the standard Bayer mosaic pattern by a non-absorbing clear material. This type of clear pixel can boost the sensor light sensitivity by a factor of more than two, thereby significantly improving the medium and low-light performance. However, this type of color scheme is partially subtractive and therefore can require the use of relatively high color correction coefficients. In addition, the high sensitivity of the clear pixel can result in a color channel imbalance that is typically corrected using relatively high white-balance coefficients. Thus, if care is not taken, proper color correction using these types of color correction and white-balance coefficients can result in an enhancement of pixel noise.
It would therefore be desirable to be able to provide improved imaging systems.